[Qemu-devel] [PATCH 09/18] nbd: Share common reply-sending code in server

[Eric Blake <eblake@redhat.com>]

Rather than open-coding NBD_REP_SERVER, reuse the code we
already have by adding a length parameter.  The code gets
longer because of added comments, but the refactoring will
make adding NBD_OPT_GO in a later patch easier.

Signed-off-by: Eric Blake <eblake@redhat.com>
---
 nbd/server.c | 59 +++++++++++++++++++++++++++++------------------------------
 1 file changed, 29 insertions(+), 30 deletions(-)

diff --git a/nbd/server.c b/nbd/server.c
index c8666ab..69724c9 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -192,12 +192,15 @@ static ssize_t nbd_negotiate_drop_sync(QIOChannel *ioc, size_t size)

 */

-static int nbd_negotiate_send_rep(QIOChannel *ioc, uint32_t type, uint32_t opt)
+/* Send a reply header, including length, but no payload.
+ * Return -errno to kill connection, 0 to continue negotiation */
+static int nbd_negotiate_send_rep_len(QIOChannel *ioc, uint32_t type,
+                                      uint32_t opt, uint32_t len)
 {
     uint64_t magic;
-    uint32_t len;

-    TRACE("Reply opt=%" PRIx32 " type=%" PRIx32, type, opt);
+    TRACE("Reply opt=%" PRIx32 " type=%" PRIx32 " len=%" PRIu32,
+          type, opt, len);

     magic = cpu_to_be64(NBD_REP_MAGIC);
     if (nbd_negotiate_write(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
@@ -214,7 +217,7 @@ static int nbd_negotiate_send_rep(QIOChannel *ioc, uint32_t type, uint32_t opt)
         LOG("write failed (rep type)");
         return -EINVAL;
     }
-    len = cpu_to_be32(0);
+    len = cpu_to_be32(len);
     if (nbd_negotiate_write(ioc, &len, sizeof(len)) != sizeof(len)) {
         LOG("write failed (rep data length)");
         return -EINVAL;
@@ -222,39 +225,35 @@ static int nbd_negotiate_send_rep(QIOChannel *ioc, uint32_t type, uint32_t opt)
     return 0;
 }

+/* Send a reply header with default 0 length.
+ * Return -errno to kill connection, 0 to continue negotiation */
+static int nbd_negotiate_send_rep(QIOChannel *ioc, uint32_t type, uint32_t opt)
+{
+    return nbd_negotiate_send_rep_len(ioc, type, opt, 0);
+}
+
+/* Send an NBD_REP_SERVER reply to NBD_OPT_LIST, including payload.
+ * Return -errno to kill connection, 0 to continue negotiation */
 static int nbd_negotiate_send_rep_list(QIOChannel *ioc, NBDExport *exp)
 {
-    uint64_t magic, name_len;
-    uint32_t opt, type, len;
+    uint32_t len;
+    int rc;

     TRACE("Advertising export name '%s'", exp->name ? exp->name : "");
-    name_len = strlen(exp->name);
-    magic = cpu_to_be64(NBD_REP_MAGIC);
-    if (nbd_negotiate_write(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
-        LOG("write failed (magic)");
-        return -EINVAL;
-     }
-    opt = cpu_to_be32(NBD_OPT_LIST);
-    if (nbd_negotiate_write(ioc, &opt, sizeof(opt)) != sizeof(opt)) {
-        LOG("write failed (opt)");
-        return -EINVAL;
-    }
-    type = cpu_to_be32(NBD_REP_SERVER);
-    if (nbd_negotiate_write(ioc, &type, sizeof(type)) != sizeof(type)) {
-        LOG("write failed (reply type)");
-        return -EINVAL;
-    }
-    len = cpu_to_be32(name_len + sizeof(len));
-    if (nbd_negotiate_write(ioc, &len, sizeof(len)) != sizeof(len)) {
-        LOG("write failed (length)");
-        return -EINVAL;
-    }
-    len = cpu_to_be32(name_len);
+    len = strlen(exp->name);
+    rc = nbd_negotiate_send_rep_len(ioc, NBD_REP_SERVER, NBD_OPT_LIST,
+                                    len + sizeof(len));
+    if (rc < 0) {
+        return rc;
+    }
+
+    len = cpu_to_be32(len);
     if (nbd_negotiate_write(ioc, &len, sizeof(len)) != sizeof(len)) {
-        LOG("write failed (length)");
+        LOG("write failed (name length)");
         return -EINVAL;
     }
-    if (nbd_negotiate_write(ioc, exp->name, name_len) != name_len) {
+    len = be32_to_cpu(len);
+    if (nbd_negotiate_write(ioc, exp->name, len) != len) {
         LOG("write failed (buffer)");
         return -EINVAL;
     }
-- 
2.5.5